LeetCode - Unique Paths II

Unique Paths II

//
public int uniquePathsWithObstacles(int[][] obstacleGrid) {
         if(obstacleGrid == null || obstacleGrid.length == 0 || obstacleGrid[0].length == 0)
            return 0;
        int m = obstacleGrid.length, n = obstacleGrid[0].length;
        int[] res = new int[n];
        if(obstacleGrid[0][0] == 0) res[0] = 1;
            else res[0] = 0;
        for(int i=0;i<m;i++)
        {
           if(obstacleGrid[i][0] == 0) res[0] = res[0];
            else res[0] = 0;
            
            for(int j=1;j<n;j++)
            {
               if(obstacleGrid[i][j] == 1){
                   res[j] = 0;
               }else{
                   res[j] += res[j-1];
               }
            }
        }
        return res[n-1];
    }
    
// better solution 
public int uniquePathsWithObstacles(int[][] obstacleGrid) {
        int m = obstacleGrid.length;
        int n = obstacleGrid[0].length;
        int[][] mat = new int[m+1][n+1];
        mat[0][1] = 1;
        for(int i=1; i<=m; i++){
            for(int j=1; j<=n; j++){
                if(obstacleGrid[i-1][j-1]!=1)
                    mat[i][j] = mat[i-1][j]+mat[i][j-1];
            }
        }
        return mat[m][n];
    }